Up in Snow Country, many places have been hit with the first (or second or third!) snow storm of the year. And with snow, some people need to worry about ice on the roof. As young Carrick pointed out in the video from my last post, frost and snow patterns on roofs can help give us clues about how a house is working. And you should be concerned if you ever have large icicles, water spots forming in your ceiling, damp attics or related problems. Ice and ice damming can wreck your roof and can expensive damage to you house and furnishings. 
What is Ice Damming?
Ice dams are typically caused by poor or missing insulation and air leakage from your house into your attic. In the winter, this warms the roof and causes the snow to melt. The melting snow then moves down the roof slope until it reaches the cold overhang, where it refreezes.
The process forms icicles and can actually create a dam that eventually forces the water to back up under the shingles and sometimes into the ceiling or wall inside the home. In addition to roof and water damage, ice dams can cause structural decay and mold and mildew to form in attics and on wall surfaces.
The Fix
Fortunately, you can dramatically reduce damage from ice damming by sealing the holes connecting your heated living space and the attic, as well as properly insulating your attic. There are different techniques to stop air leaking through recessed lights, leaky heating ducts, attic access doors, and plumbing and electrical penetrations. Sealing these leaks keeps warm air in your house were it belongs. Together, with adequate levels of insulation, this greatly reduces the chance of ice damming and large icicles. You do NOT just want to add more insulation before sealing the air leaks—this can actually create additional problems that can also damage your roof. You can’t eliminate icicles completely. Small icicles are normal. And some roof architecture–especially big valleys draining to a small corner–are especially challenging. But if you have long icicles or thick heavy ice you should act quickly to prevent damage. (And this means preventing the ice from forming in the first place, not risk life, limb, and your roof trying to chip off ice that’s there.)
Do it right. Find the important leakage points and seal them up. Then add a lot of insulation. And afterwards, as with any time you change the way your house works, have your combustion appliances tested to make sure they’re operating safely and efficiently.
An added benefit to this, of course, is you’ll save energy, save money, and be more comfortable in your home, too!
Stay warm.
-Mike
